Some traits show no phenotypic plasticity, even though it seems that it would always be advantageous to be able to respond to environmental cues. So why are some traits not plastic?
For example, genetically identical plants grown in sun versus shade will soon look very different from one another. It turns out that some species are more plastic than others. Until now, we have not been able to determine what kinds of genes determine whether or not an organism displays phenotypic plasticity. A previous study measured variation in activity level for each of the roughly 6000 genes found in yeast across a range of stressful environments. Some genes varied enormously in their expression levels from one environment to the next, while others were relatively constant. That is, some genes were more plastic than others. It has now been discovered that the more regulators a gene has, the more plastic the gene. Furthermore, the plasticity of a gene depends on its function. From these simple patterns, we gain insight into the complex genetic architecture that determines how well an organism can respond to environmental change. So, some genes are so vital that they are tightly regulated and not plastic and others are more flexible (plastic).
